Power supply systems are commonly used for supplying electrical power to a load. The load is here a DC load, for example a computer server, several computer servers, a data center etc. The DC load may also be telecommunication equipment, military equipment etc. Such DC loads require a stable and reliable DC power.
In FIG. 1, a typical prior art power supply system with a power supply system module PSS is shown. The power supply system module has two AC input terminals AC1, AC2 and positive and negative DC terminals DCP, DCN. The DC terminals are connected to a DC bus which again are connected to the load.
An AC power source, typically the mains, is input to the power supply system. The power supply system module typically comprises an AC-DC converter and a DC-DC converter for providing a stable and reliable DC power to the load. One such high efficient power supply system module is known from WO 2009/028954 having a boost converter for power factor correction (PFC) and an LLC synchronous DC-DC converter. This technology is also known from the FlatPack2 HE product series, sold and marketed by Eltek ASA.
The power supply system module also comprises minimum one control circuit, typically a digital signal processor (DSP) for controlling the boost converter and the LLC converter. Each such power supply system module PSS is provided within a housing with connection interfaces for connection to a DC bus, an AC bus and possibly also a communication bus (typically based on communication bus standards, such as CAN, RS485, I2C etc).
The load may also need backup power to ensure UPS capabilities (Uninterrupted Power Supply) in case of failures in the AC mains. The backup power may comprise a DC backup, typically a battery device, supplying DC power to the DC bus. The backup power may also comprise an AC backup, for example a diesel generator, for connection to the power supply system module PSS via an AC switchgear.
In FIG. 2, a typical installation is illustrated schematically with several power supply system modules PSS connected between an AC bus and the DC bus. Several batteries are connected to the DC bus as DC backup, and several DC loads are connected to the DC bus again.
Batteries, such as lithium-ion and lead acid batteries, may explode or catch fire due to overheating, short-circuiting or over-charging. Therefore, a battery controller is needed for each battery or each group of batteries, in order to disconnect them if certain situations occur. Moreover, if one battery explodes or catches fire, there is a risk that adjacent batteries also explode due to their temperature increase caused by the first incident and cause a chain reaction.
Hence, information about battery voltage, battery current and battery temperature are normally periodically or continuously sent to the battery controller in order to monitor the status for each battery. In addition, the battery may have an incorporated safety circuit which is configured to disconnect that battery from the DC bus in order to prevent accidents. In FIG. 2, the DC backup comprises a switch for connection to and disconnection from the DC bus based on a signal from the battery controller.
Data centers may comprise a plurality of cabinets each having a plurality of power supply system modules and a plurality of DC loads in the form of servers. Such data centers are modular systems, where power supply system modules, batteries and/or servers can be added, removed or replaced dependent on the demand.
Designing power supply to a data center is challenging. There are many technical considerations that should be taken into account, for example:                reduce space of components in order to save floor space        reduce number of components in order to save floor space        increase efficiency of components in order to reduce the electricity costs        balance the need of backup batteries (data centers need a backup capacity for 30-60 seconds, using too many batteries are expensive, and using too few batteries are also expensive due to risk for increased down time for the servers)        reduce manual work (large data centers may have as many as 2-3000 battery controllers that must be installed manually)        increase safety by reducing risk of battery accidents, and especially to reduce the risk of several adjacent batteries failing.        
The object of the invention is to provide an improved power supply system module for use in a power supply system, where the total power supply system consumes less space, which requires less time to be installed and where safety is increased.